For the past 5 billion years, the expansion of the universe has been powered by a mysterious repulsive force known as dark energy. Now, thanks to a new technique for measuring the three-dimensional structure of the distant universe, scientists in an international team within the Sloan Digital Sky Survey (SDSS-III), including an astronomer at Penn State, have made the first measurement of the rate of this cosmic expansion as it was just 3 billion years after the Big Bang. "Observations in the past 15 years have revealed that the expansion rate of the universe is accelerating," said Donald Schneider, Distinguished Professor of Astronomy and Astrophysics at Penn State, a coauthor of the study. "Most cosmological models predict that when the universe was young, dark energy had little influence on the expansion; at that time the evolution of the large-scale structure of the universe was dominated by gravitation, which is an attractive force that acted to slow the expansion. The new SDSS-III observations are an important probe of this early era."

The case of the missing quasar gas clouds has been solved by a worldwide research team led by Penn State astronomers Nurten Filiz Ak and Niel Brandt. The discovery is being announced Oct. 1 in a paper published in The Astrophysical Journal, which describes 19 distant quasars whose giant clouds of gas seem to have disappeared in just a few years. "This research is really exciting for me," Filiz Ak, a graduate student in the Department of Astronomy and Astrophysics at Penn State and lead author of the paper, said. "I'm sitting at my desk, discovering the nature of the most powerful winds in the Universe."

The Sloan Digital Sky Survey (SDSS-III) has announced the most accurate measurements yet of the distances to galaxies in the faraway universe, giving an unprecedented look at the time when the universe first began to expand at an ever-increasing rate.

The results, announced at a press conference in Manchester, England, are the culmination of more than two years of work by the team of scientists and engineers, including a Penn State astronomer, behind the Baryon Oscillation Spectroscopic Survey (BOSS), one of the SDSS-III's four component surveys.

The scientists of the Sloan Digital Sky Survey (SDSS), including astronomers at Penn State, have produced a new map of the universe that is in full color, covers more than one quarter of the entire sky, and is full of so much detail that you would need five-hundred-thousand high-definition TVs to view it all. The map consists of more than one-trillion pixels measured by meticulously scanning the sky with a special-purpose telescope located in New Mexico. This week, at the annual meeting of the American Astronomical Society in Austin, Texas, the SDSS scientists announced results of four separate studies of this new map that, taken together, provide a history of the universe over the last six-billion years.

A powerful new tool for probing the structure of our galaxy has been developed by astronomers associated with the Sloan Digital Sky Survey, including two Penn State astronomers. The new tool is an infrared spectrograph for the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Over the next three years, APOGEE's initial census of the chemical constitution and motion of more than 100,000 stars across the Milky Way will bring together data on stars with ages spanning nearly the full age of the universe.

Our Milky Way Galaxy continues to devour its small neighboring dwarf galaxies, reports a research team that includes a Penn State astronomer. The scientists have found evidence of the stellar snacking spread out across the sky. "Our study gives further striking evidence that we live in a galaxy that is constantly changing its structure via cannibalism of its smaller neighbors," said Donald Schneider, Distinguished Professor of Astronomy and Astrophysics and a coauthor of the paper describing the discovery.

A new report, prepared for the National Academy of Sciences by the National Research Council, ranked the Large Synoptic Survey Telescope (LSST) as the top U.S. priority for the next large ground-based astronomical facility. "The LSST is one of the most ambitious ground-based astronomical projects ever undertaken," said Larry Ramsey, head of Penn State's Department of Astronomy and Astrophysics and a member of the LSST Board of Directors. "It promises to provide fundamental advances in many fields of astrophysics, from the identification of potential 'killer asteroids' to the global properties of the universe." The 8.4-meter LSST telescope, to be placed on a mountain in northern Chile, will be equipped with the world's largest digital camera -- 3.2 billion pixels -- to construct a color "movie" of the entire visible sky for studying changes in movement or brightness.

Penn State astronomers Peter Meszaros and Donald Schneider are among the scientists whose research has the most scientific impact worldwide, according to ScienceWatch, an organization that monitors performance in basic research. Meszaros, holder of the Eberly Family Chair in Astronomy and Astrophysics and a professor of physics, was ranked recently as the most highly-cited scientist in the field of gamma-ray-burst astronomy throughout the past decade. Schneider, distinguished professor of astronomy and astrophysics, was cited as among the 13 scientists in all scientific disciplines who have the largest number of high-impact papers from 2007 to 2008.

"Dark energy," says Donald Schneider, professor of astronomy at Penn State, "appears to be the major component of the universe." It's not the same thing as dark matter: ordinary planets, rocks, dust, and particles that do not emit light and therefore cannot be easily detected. It's something fundamentally different, outside our current understanding of physics—a substance totally new to science.

The Milky Way Galaxy has lost weight. A lot of weight. About a trillion Suns' worth, according to an international team of scientists from the Sloan Digital Sky Survey (SDSS-II), whose discovery has broad implications for our understanding of the Milky Way.

"No," is what Albert Einstein would likely say if he was alive today—and he would be the man to ask, because scientists have been taking his word for it ever since the early 20th century.

According to Einstein's theory of special relativity, published in 1905, nothing can exceed the speed of light. That speed, explained Einstein, is a fundamental constant of nature: It appears the same to all observers anywhere in space.